slice.hpp

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// SPDX-License-Identifier: BSD-3-Clause
/* Copyright 2018-2020, Intel Corporation */
 
#ifndef LIBPMEMOBJ_CPP_SLICE_HPP
#define LIBPMEMOBJ_CPP_SLICE_HPP
 
#include <iterator>
#include <stdexcept>
#include <type_traits>
 
#include "detail/template_helpers.hpp"
 
namespace pmem
{
 
namespace detail
{
template <typename Iterator>
using subtraction =
    decltype(std::declval<Iterator>() - std::declval<Iterator>());
template <typename Iterator>
using has_subtraction = supports<Iterator, subtraction>;
 
template <typename Iterator>
using pre_decrement = decltype(std::declval<Iterator>().operator--());
template <typename Iterator>
using has_pre_decrement = supports<Iterator, pre_decrement>;
 
template <typename Iterator>
using indexing = decltype(std::declval<Iterator>().operator[](
    std::declval<
        typename std::iterator_traits<Iterator>::difference_type>()));
template <typename Iterator>
using has_indexing = supports<Iterator, indexing>;
} /* namespace detail */
 
namespace obj
{
 
template <typename Iterator>
class slice {
public:
    using size_type = std::size_t;
    using iterator = Iterator;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using reference = typename std::iterator_traits<iterator>::reference;
 
    slice(Iterator begin, Iterator end) : it_begin(begin), it_end(end)
    {
        static_assert(
            std::is_pointer<Iterator>::value ||
                (detail::has_indexing<Iterator>::value &&
                 detail::has_pre_decrement<Iterator>::value &&
                 detail::has_subtraction<Iterator>::value),
            "Iterator should support: operator[], operator-(), operator--()");
 
        if (it_end - it_begin < 0)
            throw std::out_of_range("pmem::obj::slice");
    }
 
    slice(const slice &other) noexcept = default;
 
    slice &operator=(const slice &other) noexcept = default;
 
    iterator
    begin() const noexcept
    {
        return it_begin;
    }
 
    iterator
    end() const noexcept
    {
        return it_end;
    }
 
    reverse_iterator
    rend() const noexcept
    {
        return reverse_iterator(it_begin);
    }
 
    reverse_iterator
    rbegin() const noexcept
    {
        return reverse_iterator(it_end);
    }
 
    reference
    at(size_type idx)
    {
        if (idx >= size())
            throw std::out_of_range("pmem::obj::slice");
 
        return it_begin[static_cast<typename std::iterator_traits<
            Iterator>::difference_type>(idx)];
    }
 
    reference operator[](size_type idx)
    {
        return it_begin[static_cast<typename std::iterator_traits<
            Iterator>::difference_type>(idx)];
    }
 
    size_type
    size() const
    {
        return static_cast<size_type>(it_end - it_begin);
    }
 
private:
    iterator it_begin, it_end;
};
 
} /* namespace obj */
 
} /* namespace pmem */
 
#endif /* LIBPMEMOBJ_CPP_SLICE_HPP */